Structural instabilities for YBa1.8La0.2Cu3Oy near the superconducting transition temperature

Thermal expansion measurements of (Cu0.25Tl0.75)-1234 added by MgO-nano particles

“…Also, we can not assure any anomalies (jump) in the variation of˛with T closer to superconducting transition temperature. This behavior is similar to that of the temperature dependence of the specific heat measurements of Bi-2212 and Tl-1223 phases [22,23], that did not show any jump in the specific heat at T c . The anomalies in˛closer to T c is attributed to the oxygen nonstoichiometery, for (Bi, Pb)-2223 [6] or to the polaron formation phenomena of YBaCuO [24].…”

Thermal expansion measurements using x-ray powder diffraction of Tl-1223 substituted by molybdenum

“…This means that the thermal expansion behaviour can be divided into two regions. The first is the region of linear behaviour of the temperature dependence of resistivity for temperatures greater than T c , whereas the second one is the superconducting and pseudo gap opening region [15]. Also, we cannot be certain of any anomalies (jump) in the variation of α with T closer to superconducting transition temperature.…”

Out-of-plane ionicity versus in-plane covalency interplay in high-T c cuprates

“…6) may be clearly seen. The OP catastrophe (the ionic polarization catastrophe) can be considered as the origin of many structural instabilities and anomalies that have been observed by many research groups using different experimental methods in YBa 2 Cu 3 O 6.9 as well as other high-temperature superconductors near the critical temperature T c (Schä fer et al, 1988;Srinivasan et al, 1988;Horn et al, 1987;Cheng et al, 1994;Molchanov & Simonov, 1998;Xu et al, 1991;Wu et al, 2001;Zhang et al, 2008;Buttner et al, 1992). The signature of this local field catastrophe in YBa 2 Cu 3 O 6.9 is the discontinuity in the Ba-O4 bond length along the c axis, observed at the superconducting transition temperature as illustrated in Fig.…”

“…Also the LO phonon dispersion observed by inelastic neutron scattering measurements on YBa 2 Cu 3 O 7-δ (YBCO) suggests that the frequencies of the LO phonons are strongly softened with doping near the zone boundary [28]. The local field avalanche (the ionic polarization catastrophe) can be considered as the origin behind many structural instabilities and anomalies that have been observed by many research groups using different experimental methods [18,[29][30][31][32][33][34][35][36] in YBa 2 Cu 3 O 6.9 as well as other HTS near the critical temperature T c .…”